Cold weather chickens – 8 things NOT to do to in winter!!...Personally, I think over-warming the coop should be #1 ~ the warmer the coop, the colder it seems outside & the harder it is to acclimate to that cold.
Chicken Waterer Heater - no more frozen water! Use an old cinder block that has a stepping stone on the top as a cover. Inside one cavity of the cinder block add a light bulb. The light bulb puts off just enough heat to keep the concrete block warm. The waterer then sits on top of the concrete and keeps it just warm enough not to freeze.